Refuelable electrochemical battery

ABSTRACT

A refuelable electrochemical battery is provided that features three phases of operation that repeat cyclically. In an intake phase a mixture of electrochemically active particles or pellets (e.g., aluminum pellets) and a suitable electrolyte (e.g., sodium hydroxide, potassium hydroxide) are fed into a cavity or chamber. In a power phase the resulting electrochemical reaction produces electrical energy. The particles are mechanically combined or collected to form one electrode, while a gas-diffusion membrane permeable by oxygen is another electrode. During the exhaust phase, a piston forces the residue of the reaction from the cavity in order to prepare for the next cycle of operation.

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/830,449, which was filed Jun. 3, 2013 and is incorporated hereinby reference.

BACKGROUND

A refuelable electrochemical battery (or cell) and methods of refuelinga refuelable electrochemical battery are provided.

Primary and secondary types of batteries or cells have long been used aspower sources. A primary battery is generally meant for one-time use, isnot rechargeable, and may or may not be recycled. A secondary battery isrechargeable via a process in which the electrochemical process by whichelectrical energy was generated is reversed. For example, somelithium-ion and nickel-cadmium batteries can be recharged by applying anelectrical current.

In addition, reconstructible metal/air batteries have been developedthat take advantage of the high energy density of some metals (e.g.,zinc), but which must be removed from the equipment they power in orderto be refueled and refurbished. For example, Cooper (U.S. Pat. No.5,434,020) provides a zinc/air battery that must be uninstalled andprocessed in order to replace the expended metal particles.

Other metal/air batteries, or fuel cells, are refillable via a processthat relies upon gravity to ensure proper settling of the metalparticles and formation of the metal electrode. For example, Gutierrez(U.S. Pat. No. 6,162,555) provides for feeding particles into cellcavities via flows shaped parallel to the cavities. However, these typesof batteries are vulnerable to decreased efficiency resulting fromclogging of valves, pores, and/or other conduits designed to allowcirculation of the particles and/or an electrolyte. In particular, assome particles are expended, a sludge or paste tends to be formed thatcan prevent further or complete oxidation of the remaining particles.Attempts have been made to avoid this problem, but still rely upongravity to combine the metal particles.

Existing metal/air batteries that rely upon gravity to feed metalparticles into a cell are vulnerable to loss of power and/or decreasedefficiency if they are disturbed or oriented such that gravity actsagainst the necessary flow of the particles or electrolyte.

SUMMARY

In some embodiments of the invention, a refuelable electrochemicalbattery is provided that employs mechanical force to aggregate orcombine electrochemically active (e.g., metal) particles as oneelectrode. A gas-diffusion membrane permeable to oxygen acts as theother electrode. The particles are delivered to the cell mixed with oreven suspended within a suitable electrolyte.

Operation of the battery involves three stages in some embodiments. Anintake stage involves pumping or drawing the fuel (i.e., theelectrolyte/particle mixture) into a cell. A power stage commences afterthe cell is full, or nearly full, as the mechanical force combines orcollects the particles and an electrical current is formed bydissolution (e.g., oxidation) of the electrochemically active material.An exhaust stage is initiated when the current fails or falls below athreshold level, involves expulsion of the spent electrolyte (and anyremaining particulate matter), and terminates with initiation of anotherintake stage.

DESCRIPTION OF THE FIGURES

FIG. 1 is a front view of a refuelable electrochemical battery, inaccordance with some embodiments of the invention.

FIG. 2 is a top view of the refuelable electrochemical battery of FIG.1, in accordance with some embodiments of the invention.

FIG. 3 is a right-side view of the refuelable electrochemical battery ofFIG. 1, in accordance with some embodiments of the invention.

FIGS. 4A-B are top views of a refuelable electrochemical battery inaccordance with some embodiments of the invention.

FIG. 5 is a flow chart illustrating a method of refueling a refuelableelectrochemical battery, in accordance with some embodiments of theinvention.

FIGS. 6A-B are top and front views of a refuelable electrochemicalbattery, in accordance with some embodiments of the invention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the invention. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the scope of thepresent invention. Thus, the present invention is not intended to belimited to the embodiments shown.

In some embodiments of the invention, a refuelable electrochemicalbattery is provided. The battery is refuelable in place, meaning that itneed not be removed from its operating position in order to be refueled.In these embodiments, the battery is refueled with a mixture thatcomprises electrochemically active particles and a suitable electrolyte.In an illustrative implementation, the particles are pellets ofaluminum, zinc, or some other metal having relatively high energydensity, while the electrolyte may be sodium hydroxide or potassiumhydroxide. In other implementations, the particles may be any one ofvarious other elements, minerals, or compounds, and the electrolyte maybe any other suitable electrolyzing liquid (e.g., saltwater, vinegar).

In some embodiments, operation of a refuelable electrochemical batteryinvolves three stages or phases: intake, power, and exhaust. During theintake stage, the fuel is drawn or pumped into a cavity through anintake port. During the power stage, the battery produces electricalenergy, possibly on the order of magnitude of 1000 watt-hours perkilogram of fuel or electrochemically active material. During theexhaust phase the spent electrolyte and any residue (e.g., zincate,aluminum oxide) is expelled through an exhaust port in order to preparefor another intake stage.

The electrochemically active particles are aggregated or combined toform one electrode (e.g., the anode) or part of one electrode, while theother electrode (e.g., the cathode) is a gas-diffusion membrane that maybe in contact with (on one surface) the fuel and that therefore allowsoxygen to enter the cavity and react with the fuel. Conductive transferplates, ribs, struts or other means may be used to assist the currentflow. Instead of relying upon gravity to pack the particles into achemically active or reactive bed, in some embodiments mechanical meansare used to collect them and possibly force them into contact with anelectrode (e.g., anode) current collector.

In some implementations, for example, a collector component of thebattery begins collecting the electrochemically active particles afteror at the end of the intake phase, in order to facilitate the powerphase. As the particles dissolve, the collector may continue to applypressure to the remaining particles in order to support continued powergeneration. At the end of the power phase, the collector retracts orwithdraws to allow the exhaust phase to proceed. The collector maycomprise a plunger, a gate, an arm, a brush, a wedge, a lever, and/orsome other means that mechanically gathers or collects theelectrochemically active particles.

In some other implementations, a battery or a battery cavity may rotateduring operation (i.e., during the power phase), with sufficientvelocity to aggregate or force heavier electrochemically activeparticles (e.g., those that have dissolved less) to the outer wall(s) ofthe cavity due to centrifugal force. The residue may thereby be forcedinto the central portion, from which it may be expelled or extracted. Insome implementations, the rotation may assist with expulsion of theresidue during the exhaust phase.

In some embodiments, the same or different mechanical means used tocollect the electrochemically active particles may operate to empty thecavity during the exhaust phase. For example, a piston or piston-likecomponent may physically force the residue from the battery cavity, andretract to allow or even facilitate refilling of the cavity with freshfuel.

In some embodiments, the fuel may be a suspension in which the particlesare on the order of 1 mm average diameter and are dispersed within theliquid electrolyte. In these embodiments, assuming approximately uniformdistribution of the particles in the liquid, pumping a given volume ofthe fuel into the battery cavity will ensure an appropriate ratio ofelectrolyte to electrochemically active particles. In other embodiments,the electrochemically active particles are larger and, instead of beinguniformly dispersed within the electrolyte, naturally aggregate at thebottom of whatever vessel contains the fuel. In these embodiments, thecorrect proportion of electrochemically active substance to electrolytemay be ensured by separately feeding the electrolyte and the particlesto the battery, or by pre-combining them in the correct amounts prior to(or during) each intake phase.

Due in part to the manner in which the electrochemical battery isrefueled or replenished, it may be termed an “electrical generator,” an“electromechanichemical engine,” a “tertiary cell” (to differentiate itfrom primary and secondary cells), or may be given some other monikerthat reflects its ability to generate electrical energy from anelectrochemical process that employs some mechanical force and that isrefuelable in place.

In some embodiments, a refuelable electrochemical battery providedherein comprises multiple cells or cavities, such as a bipolar batteryin which electrodes are connected in series or in parallel. In addition,multiple separate batteries or battery packs may be provided forpowering a load, wherein at least one battery supports the other(s) bypowering its/their mechanical component(s), powering the intake andexhaust phases, facilitating a transition from powering the load fromone collection of cells to powering the load from a different collectionof cells, etc. A combination of multiple batteries may, for example, beformed into two-dimensional or three-dimensional array, depending onweight limits, available space, battery size, etc.

The load that is powered by a refuelable electrochemical battery may beany type of device or equipment that operates on electrical energy.Illustratively, if the load is a vehicle it may be periodically drivento a refueling station that refills a storage tank of the vehicle withfuel and that may receive accumulated residue (e.g., for processing intoadditional fuel).

FIG. 1 is a diagram of a refuelable electrochemical battery, accordingto some embodiments of the invention.

In these embodiments, battery 100 comprises cavity 116 defined by walls110, and is generally cylindrical in shape (e.g., ellipsoidal (as shownin FIG. 2), circular). The intake phase of operation of battery 100 ismarked by a flow of fuel through intake port 112 from a storage tank.Conversely, the exhaust phase is marked by the expulsion of residuethrough exhaust port 114. Piston 118 assists in the expulsion of theresidue. In some implementations, the upper wall of the battery (whichhosts ports 112, 114) slopes outward and upward slightly to assist inthe evacuation of cavity 116; in other implementations, and as shown inFIG. 1, the exhaust port is offset from the upper wall in addition to orinstead of a sloping upper wall.

Cathode 120 is oxygen-permeable, from an air side external to battery100 and into cavity 116, wherein the oxygen can react with the fuelmixture to feed the electrochemical action. Thus, one (interior) surfaceof cathode 120 forms part of wall 110, and may be wettable by the fuelmixture. In some implementations, however, an insulating separator(e.g., a wettable fabric) covers the interior surface of cathode 120 butdoes not impede (or does not significantly impede) the current flow. Oneor more conductive components (e.g., plates, ribs, struts, strips,ribbons) may assist current flow toward the cathode.

Collector 130, which is connected to arm 132 for extending or retractingthe collector, is shown in a partially deployed or extended orientation.As is more clearly shown in another figure, the collector may comprise aflexible and relatively sturdy mesh or perforated surface through whichthe liquid electrolyte can pass, but which collects electrochemicallyactive particles that are larger than the perforations, and presses themto or toward air cathode 120.

In some implementations, collector 130 is metallic and acts as a currentcollector. In some other implementations and as indicated above, asimilar (anode) current collector is provided in the form of a plate, amesh, or other conductive transfer surface(s) situated adjacent to andin contact with a porous insulating separator that, in turn, covers aircathode 120 (internal to battery 100). Thus, the (anode) currentcollector(s) collects electrical charges emitted by theelectrochemically active particles as they dissolve, and transfers themtoward cathode 120. Although not shown in FIG. 1, one (positive) currentlead may be coupled to or embedded within air cathode 120, and another(negative) lead may be coupled to collector 130, arm 132, or some otheranode current collector or transfer entity that is coupled to theelectrochemically active particles.

During the intake phase of battery 100, piston 118 withdraws from theupper wall, or is already in the retracted position shown in FIG. 1before the intake phase begins. After cavity 116 has been(substantially) filled with fuel, or a predetermined amount of fuel hasbeen introduced into cavity 116, piston 118 is in the position shown inFIG. 1 and collector 130 extends toward air cathode 120 in order tosweep the electrochemically active particles of the fuel toward thecathode and to place them in contact with a current collector ortransfer component.

After a predetermined period of time, or after the electrical output ofthe battery fails or falls below a predetermined level, or upon someother trigger, collector 130 retracts to and/or flush with a wall 110.The exhaust phase then commences with piston 118 moving upward (in theembodiments of FIG. 1) to force the residue and any remaining fuel fromcavity 116, after which another intake phase begins.

In some implementations, collector 130 extends and retracts in responseto extension and retraction of arm 132 (e.g., a screw, a rod), which maybe powered by a different battery. In some implementations, instead ofarm 132, which may pierce a wall 110 of the battery, means for extendingand retracting collector 130 may be completely internal to the battery,such as a mechanism similar to a scissors lift. In otherimplementations, a collector component has a different form altogether(e.g., one or more movable gates or panels).

In yet another implementation, multiple arms 132 are used to makecontact with multiple areas of collector 130 instead of a single joint.In a further implementation, arm 132 has a much greater height orvertical dimension so that instead of apply mechanical force on just asmall area of collector 130, it contacts the collector along themajority of the collector's height, and may be envisioned as a wall thatis orthogonal to collector 130 as shown in FIG. 1.

Some components of a refuelable electrochemical battery, or of a batterysystem or apparatus are omitted. For example, a digital processor may becoupled to the battery to control its operational cycles and phases,wires or other conductors carry the electrical current, a piston rod orother connecting element couples piston 118 to a cam or other mechanismfor operating the piston, etc. The exterior casing of battery 100(including walls 110) may be constructed of a heavy duty plastic orother non-conductive material.

FIGS. 2 and 3 are top and right-side views, respectively, of therefuelable electrochemical battery of FIG. 1, according to someembodiments of the invention.

FIG. 2 shows air cathode 120 adjacent to a portion of the surface of awall 110, and may extend for any portion of the vertical height of thebattery. Generally, however, a bottom edge of cathode 120 is coplanarwith a top edge or surface of piston 118 when the piston is retracted asshown in FIG. 1. The dimensions of the gas-diffusion membrane of aircathode 120 may vary from one implementation to another, depending onthe necessary transfer rate of oxygen, for example.

Also as shown in FIG. 2, flexible collector 130 may have dimensions suchthat it is approximately full extended vertically and horizontally (in asubstantially rectangular shape) when it is located near the midpoint ofthe battery's cavity. Illustratively, it may bend to conform to thecontour of the interior surface of the battery as it extends orretracts, such that it may have a convex aspect when fully extended (orretracted) and a concave aspect when fully retracted (or extended). Insome embodiments, cavity 116 may feature horizontal groves and edges ofcollector 130 may feature extensions that ride in the grooves to guideit during extension/retraction. In some embodiments in which thecollector component acts as a current collector, it may transfer thatcurrent through conductive ribs or guides within the grooves and toanother current collector near or adjacent to cathode 120. Currentcollected by the collector may be conducted toward the cathode in otherways in other embodiments.

As shown in FIG. 3, collector 130 of battery 100 is perforated to allowelectrolyte to pass through it as it collects the electrochemicallyactive particles to or toward air cathode 120. It may be noted that theaverage diameter of perforations 134 may be (substantially) smaller thanthe average diameter of the particles, so as to ensure collection ofvirtually all of the particles.

In some embodiments, a battery cavity may be rectangular, in which casecollector 130 of FIGS. 1-3 may be rigid, of dimensions that arecompatible with the interior of the cavity, and it may maintain auniform aspect as it is extended and retracted.

FIGS. 4A-B are top views of a refuelable electrochemical batteryaccording to some embodiments of the invention. In these embodiments,the collector component is implemented as a pair of gates 430 that sweepthe electrochemically active particles together as they aredeployed/extended. In FIG. 4A, the collectors are connected to pivots(not shown) in opposing walls 110, and have just begun to deploy fromthe positions they assume during the intake and exhaust phases, whereinthey are flush or nearly flush with the opposing walls. In FIG. 4B, thecollector gates are partially deployed (or fully deployed in someimplementations).

In other embodiments the gates are installed on other walls. Forexample, one gate may have a resting position flush with the top surfaceof piston 118, while another gate has a resting position flush with theinterior surface of a side wall of the battery.

FIGS. 6A-B are top and front views of a refuelable electrochemicalbattery, according to some embodiments of the invention. In theseembodiments, a collector comprises multiple interlocking or interlacedsweeps or combs for gathering electrochemically active particles.Together, the components filter the fuel mixture to mechanically gatherthe particles.

In the top view of FIG. 6A, intake and exhaust ports are not shown, inorder to more clearly illustrate the collector components. FIG. 6Aprovides a view of a first collector, anchored to the top of piston 618by pivot arm 650 and comprising multiple rigid or semi-rigid fingers 652separated by gaps 656. Each finger has one or more perforations 654,which may or may not be aligned as shown in the figure.

During the power phase of operation of battery 600, and as shown in thefront view of FIG. 6B, fingers 652 of the first collector interlace withfingers 662 of a second collector anchored to a wall 610 at pivot arm660. In particular, fingers 662 of the second collector fit within gaps656 of the first collector, and fingers 652 of the first collector fitwithin gaps of the second collector. The second collector may bevirtually identical to the first collector except for its orientation.In the power phase, the collector components force electrochemicallyactive particles 670 of the fuel toward air cathode 620.

In some implementations, the collector components of battery 600 alsocollect current that may be fed through pivot arms 650, 660, and mayfurther be conducted toward a current collector located near cathode 620(e.g., possibly separated by a suitable wettable insulator), perhaps viaconductors embedded in one or more walls of the battery and/or thesurface of piston 618.

FIG. 5 is a flow chart illustrating a method of refueling a refuelableelectrochemical battery, according to some embodiments of the invention.

In operation 502, the intake phase commences. In some embodiments, thismay entail opening a valve connecting a feed tube to the intake portand/or closing a valve in the exhaust port. For example, in someimplementations, only the intake port or the exhaust port can be open ata given time (and either or both may be closed during the powergeneration phase). Illustratively, a single gate or lever may rotate orotherwise move from a position blocking the exhaust port (during theintake phase) to a position blocking both ports (during the power phase)to a position blocking the intake port (during the exhaust phase), andback again as needed.

In operation 504, a predetermined mixture of a suitable electrolyte anda suitable mass of electrochemically active particles or pellets ispumped into or drawn into the battery cavity. In some implementations,withdrawal of a piston may assist in the formation of a vacuum to helpdraw the fuel into the battery. A sensor may detect when the mixture hasfilled the cavity to a suitable level, the amount of mixture deliveredmay be measured as it is fed into the cavity, or some other mechanismmay be used to determine when the cavity is sufficiently full and whenthe fuel flow should cease.

In operation 506, the power stage of the battery's operation commences.This may occur even as fuel is still being added, or may occur afterfuel delivery ceases (and the intake port is closed or blocked by aninsulating obstruction).

In operation 508, during the power stage, one or more collectorcomponents mechanically force the electrochemically active particlestogether in order to facilitate the charge flow. The collectorcomponent(s) may extend and/or retract multiple times to gatherparticles that have not been spent, and/or to stir up the electrolyte toallow continuation of the electrochemical reaction, or may extend justonce.

In some implementations, a collector component deploys incrementally tocompact or combine the particles as they dissolve and shrink in size.For example, the collector may initially deploy or extend a significantdistance and then pause when it encounters sufficient resistance (orreaches a predetermined degree or amount of extension). After someperiod of time (e.g., minutes) it may deploy further until againencountering sufficient resistance, and so on.

In operation 510, as the power output wanes (or when it ceases), thecollector component(s) retracts to its resting position. The restingposition may be configured to accommodate the exhaust phase and the nextintake phase.

In operation 512, the power phase ends as the exhaust phase commences.This operation may include opening the exhaust port or a valve or leverthat had closed the port.

In operation 514, a piston begins extending longitudinally into thebattery cavity to start forcing out the residue of the electrochemicalreaction. In some embodiments, a distal end of the piston (external tothe battery cavity) is coupled to a cam or other mechanism fortransitioning between extending the piston into the battery cavity,withdrawing from the cavity, and resting in either or both the extendedor withdrawn positions.

In operation 516, the cavity is (substantially) emptied of residue andthe exhaust port or valve may be closed. After operation 516, the methodmay end or may return to operation 502 to begin a new cycle ofoperation.

In some embodiments, the electrical energy output by a refuelableelectrochemical battery is directly fed to an active load (e.g., to runan electrically powered vehicle, to power a piece of equipment). In someother embodiments, the output is used to charge another battery or otherelectrical storage device and/or is used to provide power for conductingone or more phases of operation of another battery.

In the preceding description, ‘some embodiments’ refers to a subset ofall possible embodiments, but does not always specify the same subset ofembodiments.

An environment in which some embodiments of the invention are executedmay incorporate a general-purpose computer or a special-purpose devicesuch as a hand-held computer or communication device. Some details ofsuch devices (e.g., processor, memory, data storage, display) may beomitted for the sake of clarity. A component such as a processor ormemory to which one or more tasks or functions are attributed may be ageneral component temporarily configured to perform the specified taskor function, or may be a specific component manufactured to perform thetask or function. The term “processor” as used herein refers to one ormore electronic circuits, devices, chips, processing cores and/or othercomponents configured to process data and/or computer program code.

Methods and processes described in the detailed description can beembodied as code and/or data, which can be stored in a non-transitorycomputer-readable storage medium as described above. When a processor orcomputer system reads and executes the code and manipulates the datastored on the medium, the processor or computer system performs themethods and processes embodied as code and data structures and storedwithin the medium.

The foregoing descriptions of embodiments of the invention have beenpresented for purposes of illustration and description only. They arenot intended to be exhaustive or to limit the invention to the formsdisclosed. Accordingly, many modifications and variations will beapparent to practitioners skilled in the art. The scope of the inventionis defined by the appended claims, not the preceding disclosure.

What is claimed is:
 1. A refuelable electrochemical battery, comprising:an electrochemical cell having a cavity; an intake port for admitting amixture of a fluid and electrochemically active particles into thecavity; a collector, within the cavity, for mechanically gathering theelectrochemically active particles; and an exhaust port.
 2. Theelectrochemical battery of claim 1 wherein a portion of a wall of thecavity is composed of a non-electrically conductive gas permeablemembrane having an interior surface interior to the cavity and anexterior surface exterior to the cavity.
 3. The electrochemical batteryof claim 2, further comprising: an anode current collector; and agas-diffusion cathode in contact with the exterior surface of themembrane.
 4. The electrochemical battery of claim 3, wherein thecollector comprises the anode current collector.
 5. The electrochemicalbattery of claim 3, wherein, during operation of the electrochemicalbattery, the anode current collector traverses the cavity toward theinterior surface of the membrane.
 6. The electrochemical battery ofclaim 1, wherein: the collector is perforated; and an average diameterof the perforations is less than an average diameter of theelectrochemically active particles.
 7. The electrochemical battery ofclaim 1, further comprising: a piston having an axis collinear with anaxis of the cavity; wherein the piston moves in a first direction alongthe axis during admission of the mixture through the intake port; andthe piston moves in a second direction along the axis substantiallyopposite to the first direction to eject residue of an electrochemicalreaction within the battery through the exhaust port.
 8. Theelectrochemical battery of claim 1, wherein the collector isalternatingly extended and retracted during operation of theelectrochemical battery.
 9. The electrochemical battery of claim 8,wherein: the collector is extended through the cavity after admission ofthe mixture; and the collector is subsequently retracted substantiallycoplanar with a surface of the electrochemical battery.
 10. Theelectrochemical battery of claim 1, wherein: the electrochemicallyactive particles are particles of metal; and the fluid is an electrolytesolution.
 11. The electrochemical battery of claim 10, wherein: themetal is aluminum; and the electrolyte is one of sodium hydroxide andpotassium hydroxide.
 12. A refuelable electrochemical battery,comprising: an electrochemical cell having a cavity; an intake port foradmitting a mixture of a fluid and electrochemically active particlesinto the cavity; a filter for mechanically gathering theelectrochemically active particles; and an exhaust port.
 13. A method ofoperating the refuelable electrochemical battery of claim 1, the methodcomprising: admitting via the intake port the mixture of the fluid andelectrochemically active particles into the cavity; mechanicallycollecting the electrochemically active particles in contact with ananode current collector; drawing electrical current from theelectrochemical battery; and expelling via the exhaust port residueresulting from dissolution of the particles within the fluid.
 14. Themethod of claim 13, wherein the electrochemically active particles aresuspended in the fluid during said admitting.
 15. The method of claim13, wherein mechanically collecting the electrochemically activeparticles comprises: extending the collector into the cavity to forcetogether the electrochemically active particles.
 16. The method of claim13, wherein mechanically collecting the electrochemically activeparticles comprises: extending multiple conductive collector components,including the collector, into the cavity to force together theelectrochemically active particles.
 17. The method of claim 13, whereinexpelling residue comprises: extending a piston through the cavity toforce the residue through the exhaust port.
 18. The electrochemicalbattery of claim 7, wherein: the collector is alternatingly extended andretracted during operation of the electrochemical battery; and an axisof movement of the collector is substantially orthogonal to the axis ofthe piston.
 19. The electrochemical battery of claim 9, wherein: as thecollector is extended through the cavity and as the collector issubsequent retracted, the collector flexibly maintains contact withmultiple walls of the electrochemical cell that form the cavity.
 20. Theelectrochemical battery of claim 1, wherein: the cavity is cylindricaland is defined by a top, a bottom and a wall of the electrochemicalcell; and the intake port and the exhaust port are co-located on one ofthe top and the bottom of the electrochemical battery.